Cargo containers are commonly used to transport goods on ships, trains, and trucks. These cargo containers must be lifted and moved as they are transported. Lifting devices, such as mechanical cranes, are used to grapple and position the cargo containers. To ease coupling the lifting device to the cargo container, the cargo container may be provided with lift fittings. These fittings may be positioned in, for example, the upper or lower corners of the cargo container. Further, as the cargo container and its load may be extremely heavy, the fittings may be positioned in a reinforced area. The fittings each have at least one aperture that receives a mating portion of the lifting device. Once secured into the apertures of the fittings, the lifting device can lift and move the cargo container.
When the cargo container is in transport or storage, it may be desirable to secure the cargo container into a stable position. Therefore, locking mechanisms may be used to engage the apertures to secure the container during transport or storage. The apertures are adapted to accept lifting or locking mechanisms and to withstand the forces imposed during movement and transport.
Because cargo containers are used to transport goods throughout the United States and worldwide, national and international standards have been established for such lift fittings. For example, ISO specification 1161 provides that the fittings will be generally box-shaped without any sharp corners. Furthermore, there must be at least four fittings on the top and at least four fittings on the bottom, generally positioned at the end corners of the cargo container. Each fitting on the top should have at least one aperture on each of the exposed top, side, and end surfaces. Similarly, the fittings along the bottom edges of the cargo container should have at least one aperture on each of the exposed bottom and side surfaces.
Another typically standardized characteristic is the distance between the fittings. Containers of standard size have fittings located in the end corners, thus benefiting from the strength of the three intersecting walls at an end corner for support. Another typical standardized characteristic is the width distance between apertures of the fittings. For example a typical North American type domestic cargo container is 1023/8 inches wide, with fittings positioned in the top end corners. The aperture for each fitting is centered approximately 611/16 inches from each sidewall. In such a manner the center of a pair of apertures are spaced apart by approximately 89 inches.
However, some cargo containers are longer than the standardized lengths allowing higher-volume payloads that reduce transportation costs. These longer cargo containers generally still have four top and four bottom fittings positioned in the end corners and are approximately 1023/8 inches wide. However, the longer cargo containers also should have fittings inboard from the ends. For example, the Association of American Railroads Specification M930 specifies that cargo containers over 40 feet in length must also have four top and four bottom intermediate corner fittings positioned 40 feet apart. These fittings are attached into frames that support the loads imposed during transportation.
Many known lift fittings are difficult to manufacture, requiring the joining of parts by welding. This suffers a deficiency of substantial time and costs for production. Many known lift fittings require numerous welds to create the frame of the cargo container. This welding is also undesirable because it increases the time and costs of manufacture.
Furthermore, many known lift fittings need bulky vertical supports, creating cargo containers with non-smooth sidewalls. Smoother sidewalls are desirable because they can allow higher volume cargo payloads. Furthermore, smoother sidewalls increase the durability of the cargo container by reducing the damage caused by objects catching the edges of a non-smooth sidewall.
Accordingly, there is a need for a lift fitting that is economical to manufacture, but strong enough to survive the rigors of transportation, including lifting, stacking, and racking. There is also a need for an a lift fitting that allows the construction of cargo containers with sufficient strength but with fewer welds to reduce production costs. Furthermore, there is a need for an a lift fitting that allows the construction of a cargo container with substantially smooth sidewalls.